1. Field of the Invention
The present invention relates to print heads for ink printing devices, and more particularly to print heads for printing devices of the ink jet printer type.
2. Prior Art
In an ink jet printer, an ink supply is provided communicating with the discharge opening by way of ink channel, from which the ink is ejected in the form of droplets under the influence of a transducer. For the practical operation of such devices, as well as for their functional reliability, special requirements are important. For example, the individual ink channels of the print head which are in communication with an ink supply system for supplying the ink to the discharge openings must be precisely dimensioned in their cross-section and free of any abnormality in the vicinity of the discharge openings. Even minute irregularities can lead to a modification of the individual ink jets, or to a failure of such jets. In print heads employing a large number of jets, these problems increase considerably, because a large number of jets has special need of print heads in which the ink channels and discharge openings are small and precise, in order to give small droplets of uniform size from each discharge opening.
In accordance with the method described in German Pat. No. OS2543451, a pre-assembled unit incorporating a plurality of needles together with drive elements for the droplet ejection are inserted into an injection or casting mold before casting the print head. The ink channels are fashioned in the head after removal of the needles. This method requires a very precise assembly of the needles and associated apparatus, and must be executed by largely manual means. In order to guarantee a completely smooth surface on the inside of the ink channels, the removal of the needles must take place with great precision.
It has also been proposed, in German Pat. No. OS3108206 to construct a print head by forming ink channels and an ink feed chamber as recessed in a photosensitive layer. The photosensitive layer applied to a substrate is covered with a photomask made up of light impermeable regions to define the ink channels in the ink feed chambers. The desired recesses are then formed by means of exposure to radiation and subsequent treatment with solvent. A cover plate completes the overall arrangement. Only relatively simply structures however can be fashioned with this method. The particularly high demands which are made on the shape of the ink channels for precision in print heads for ink jet printers cannot be satisfied with this method.
It is accordingly desirable to provide a method for the manufacture of print heads which allow formation of ink channels in an arbitrary three dimensional form under circumstances which allow for automation and relatively low manufacturing costs.